Messages in this thread |  | | Subject | Re: [PATCH v2] virtio_net: CTRL_GUEST_OFFLOADS depends on CTRL_VQ | From | Jason Wang <> | Date | Mon, 6 Jan 2020 10:47:35 +0800 |
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On 2020/1/5 下午9:22, Michael S. Tsirkin wrote: > The only way for guest to control offloads (as enabled by > VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) is by sending commands > through CTRL_VQ. So it does not make sense to > acknowledge VIRTIO_NET_F_CTRL_GUEST_OFFLOADS without > VIRTIO_NET_F_CTRL_VQ. > > The spec does not outlaw devices with such a configuration, so we have > to support it. Simply clear VIRTIO_NET_F_CTRL_GUEST_OFFLOADS. > Note that Linux is still crashing if it tries to > change the offloads when there's no control vq. > That needs to be fixed by another patch. > > Reported-by: Alistair Delva <adelva@google.com> > Reported-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com> > Fixes: 3f93522ffab2 ("virtio-net: switch off offloads on demand if possible on XDP set") > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > > Same patch as v1 but update documentation so it's clear it's not > enough to fix the crash. > > drivers/net/virtio_net.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 4d7d5434cc5d..7b8805b47f0d 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -2971,6 +2971,15 @@ static int virtnet_validate(struct virtio_device *vdev) > if (!virtnet_validate_features(vdev)) > return -EINVAL; > > + /* VIRTIO_NET_F_CTRL_GUEST_OFFLOADS does not work without > + * VIRTIO_NET_F_CTRL_VQ. Unfortunately spec forgot to > + * specify that VIRTIO_NET_F_CTRL_GUEST_OFFLOADS depends > + * on VIRTIO_NET_F_CTRL_VQ so devices can set the later but > + * not the former. > + */ > + if (!virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) > + __virtio_clear_bit(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS);
If it's just because a bug of spec, should we simply fix the bug and fail the negotiation in virtnet_validate_feature()?
Otherwise there would be inconsistency in handling feature dependencies for ctrl vq.
Thanks
> + > if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) { > int mtu = virtio_cread16(vdev, > offsetof(struct virtio_net_config,
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